1. Field of the Invention
The present invention relates to an image forming apparatus provided with a cover capable of covering an image bearing member.
2. Description of the Related Art
There is known an image forming apparatus in which a vertical conveyance path for vertically conveying a transfer sheet is provided behind an opening/closing cover provided on an apparatus main body having a housing structure and a photoconductive drum is disposed at a back side facing the conveyance path. The opening/closing cover is so provided as to communicate the interior of the apparatus main body with the outside to deal with a jam of a transfer sheet in the conveyance path and other maintenance operations. Thus, if the opening/closing cover is opened, the conveyance path and various parts facing the conveyance path are exposed through an opening. For example, in the case of dealing with a sheet jam, an operator can insert his or her hand into the apparatus through the opening to easily remove the jammed transfer sheet by opening the opening/closing cover.
However, if the hand or other things touch the outer surface of the photoconductive drum during such an operation, it might cause an image formation defect due to the distortion or damage of the drum surface. Accordingly, it has been known to provide a drum cover for covering an exposed part (part facing the conveyance path) of the photoconductive drum when the opening/closing cover is at an opening position. This drum cover is retracted from the conveyance path so as not to hinder the conveyance of transfer sheets when the opening/closing cover is at a closing position.
For example, an image forming apparatus disclosed in Japanese Unexamined Patent Publication No. H06-236080 is constructed such that a rectangular drum cover P22, in which a sheet member P21 stretches on a rectangular frame P20, is so arranged above a photoconductive drum P3 as to be pivotal about a rotation axis center X1 in parallel with an axial center X of the photoconductive drum as shown in FIG. 17. The drum cover P22 pivots between positions (A) and (B) in FIG. 17 while being linked with the opening and closing of an unillustrated opening/closing cover, thereby being switched between a protecting state where the drum cover P22 protects the photoconductive drum P3 and a retracted state where the conveyance of transfer sheets is not hindered.
For example, an image forming apparatus disclosed in Japanese Unexamined Patent Publication No. 2005-91482 is constructed such that a strap P24 having one end thereof connected with an opening/closing cover and the other end thereof connected with a take-up roller P23 that dispenses and takes up the strap P24 while a biasing force is acting is provided at each of the opposite ends of a photoconductive drum P3 as shown in FIG. 18. A drum cover P26 is mounted at parts of the two straps P24 corresponding to the photoconductive drum 3 such that a flexible sheet member P25 spans between the two straps P24. The drum cover P26 is slid between positions (C) and (D) in FIG. 18 while being linked with the opening and closing of an unillustrated opening/closing cover, thereby being switched to the protecting state and the retracted state.
However, in the apparatus of Japanese Unexamined Patent Publication No. H06-236080, the drum cover P22 itself is disposed at the fixed position above the photoconductive drum P3 and needs to pivot about the rotation axis center X1 upon switching the state of the drum cover P22 between the protecting state and the retracted state. Since other members cannot be arranged in a wide range of this pivotal movement, it is necessary to leave this range as an empty space, which leads to restrictions in the arrangements of the respective mechanisms in the image forming apparatus. Since an extra space needs to be provided in the apparatus, there is another problem of enlarging the image forming apparatus.
Further, since the straps P24 and the drum cover P26 are both flexible according to the apparatus of Japanese Unexamined Patent Publication No. 2005-91482, a sliding movement can be made along a bent path and a movement path for the drum cover P26 can be set even in a small clearance in the image forming apparatus. However, if an operator's hand or the like touches the drum cover P26 in the protecting state, for example, upon dealing with a sheet jam, there is a problem of being likely to reduce a protection function due to the easy flexibility of the drum cover P26. In order to prevent this, the drum cover P26 needs to be spaced apart from the outer surface of the photoconductive drum P3 by a substantial distance. In any case, there are many restrictions in setting the movement path for the drum cover P26, leading to a problem of making it difficult to downsize the image forming apparatus.